The Truth Behind Fitness Trackers

Exercisers use various devices to track progress and determine intensity. However, recent research suggests that some trackers may not be accurate.

The goal of the study, published in Medicine & Science in Sports & Exercise (May 10, 2013; [Epub ahead of print]), was to compare how accurately various activity monitors estimated energy expenditure.

Nineteen healthy young men and women spent 4 hours in a room calorimeter, where EE could be measured from air samples.

“Participants wore a footwear-based physical activity monitor, as well as Actical, ActiGraph™, IDEEA®, DirectLife and Fitbit® devices,” the authors explained. “Each individual performed a series of postures/activities. We developed models to estimate EE from the footwear-based device, and we used the manufacturer’s software to estimate EE for all other devices.”

Data from the footwear-based device did not differ significantly from the calorimeter readings. The same was true for DirectLife and IDEEA estimates, and Actical was only slightly less accurate than IDEEA. However, the ActiGraph and Fitbit devices significantly underestimated EE.

“The shoe-based physical activity monitor provides a valid estimate of EE, while the other physical activity monitors tested have a wide range of validity when estimating EE,” the authors concluded.